Influence of absorptivity variation on Laser Powder Bed Fusion simulation and impact of process parameters on residual stress formation
Helia Mohammadkamal, Fabrizia Caiazzo
Abstract
Laser powder bed fusion stands out for its precision and capability to manufacture parts with complex geometry, yet it poses challenges due to the significant thermal gradient, causing elevated residual stress and potential damage. Ensuring precise manufacturing of Ti6Al4V, demands control over input parameters. This study employs a simulation model using COMSOL Multiphysics to explore the influence of thermal absorptivity on reliability of predicted results and role of key process parameters including laser velocity and power on temperature distribution and thermal stress. Results indicate that the volumetric heat source with temperature-dependent absorptivity, ended in more accurate predictions compared to constant absorptivity. Moreover, considering absorptivity as a function of laser power and velocity enhanced results particularly in situations with higher energy densities. However, while reducing the laser velocity and increasing laser power typically led to higher residual stress as the area exposed to high temperature was wider, there was a critical point for the impact of laser velocity, where the role of thermal gradient overcomes the role of maximum temperature.